non SGML character number %1

Cause:

You have used an illegal character in your text. HTML uses the standard UNICODE Consortium character repertoire, and it leaves undefined (among others) 65 character codes (0 to 31 inclusive and 127 to 159 inclusive) that are sometimes used for typographical quote marks and similar in proprietary character sets. The validator has found one of these undefined characters in your document. The character may appear on your browser as a curly quote, or a trademark symbol, or some other fancy glyph; on a different computer, however, it will likely appear as a completely different character, or nothing at all.

Example:

textexample textexample

Bad:
textexample
textexample
Good:
textexample textexample

Solution:

textexample textexample

References: